The invention concerns an arrangement for mass balancing in a reciprocating-piston crankshaft engine. Arrangements are known for mass balancing in a reciprocating-piston crankshaft engine in which a balancing mass is provided and is connected to move in phase opposition to the operating pistons, i.e., when the working pistons are at their lowest point the balance mass is at its highest point and vice versa. In the arrangements disclosed in DE-OS 24 23 143 and DE-OS 30 33 803, a balancing mass connecting rod is driven in opposite phase to the pistons. The balancing mass connecting rod is guided by a rocker arm pivotably connected to the balancing mass connecting rod. In these mass balancing arrangements, the rocker arms swivel on the engine housing. When the engine is in operation, the balancing mass follows a circular path, whose radius will be a function of the length of the rocker arm.